Due to more stringent environmental regulations, particularly with respect to reduced volatile organic compounds, (VOC), there is a drive within the coatings industry to switch from conventional solvent borne systems to waterborne coatings. Although aqueous polyepoxide coating systems based on polyamine adducts are known, there have been several problems associated with these systems. For example, many aqueous systems do not possess a high degree of compatibility between resin and amine components. This incompatibility can lead to an inability of the system to properly wet the substrate and form a continuous coating which, in turn, can lead to poor coating appearance and poor adhesion to the surface of the substrate. The working pot life of several commercial aqueous epoxy coating compositions can be too short and as a result systems cannot be used in certain industrial applications.
U.S. Pat. No. 5,246,984 describes water compatible polyamine adducts formed by the reaction of a polyamine with a mixture of monoepoxides and polyepoxides. The resultant mixture is further reacted with formaldehyde which results in the methylolation of the primary amine hydrogens. This is a way of reducing the primary amine content of the product so as to extend pot life in a liquid resin system.
U.S. Pat. No. 4,539,347 describes curing agents based on the reaction product from a multi-functional epoxy novolac resin and a polyamine, wherein the remaining primary amines are reacted with a monoepoxide or a monocarboxylic acid.
U.S. Pat. No. 4,246,148 discloses a polyamine terminated difunctional epoxy adduct which is end capped with a combination of both aliphatic and aromatic monoepoxides.
U.S. Pat. No. 4,608,405 describes curing agents that are based upon an epoxidized polyol containing aromatic and polyalkylene ether moieties in which all the epoxide groups are reacted with a polyamine wherein each primary amine in the resulting reaction product is further reacted with a monoepoxide or a monocarboxylic acid.
U.S. Pat. No. 4,197,389 describes curing agents prepared by the reaction of a polyepoxide compound, a polyalkylene polyether polyol and a polyamine. The adduct may be further reacted with an unsaturated compound such as acrylonitrile. Curing agents are used to form coating compositions with solid resin dispersions.